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엄혜주,박근 한국정밀공학회 2011 International Journal of Precision Engineering and Vol. No.
High-frequency induction heating is an efficient way to heat mold surfaces by electromagnetic induction using a non-contact procedure. Due to its ability to rapidly heat and cool mold surfaces, this method has been applied recently to the injection molding of micro/nano structures. The present study investigates a localized heating method involving the selective use of mold materials to enhance the heating efficiency of high-frequency induction heating. A composite injection mold consisting of ferromagnetic material and paramagnetic material was used for localized induction heating. The feasibility of this localized heating method was investigated through numerical analyses in terms of its heating efficiency for localized mold surfaces and the resulting flow characteristics in micro channels. To take into account the effects of thermal boundary conditions of localized induction heating, a fully integrated numerical analysis effectively connecting electromagnetic field calculation, heat transfer analysis, and injection molding simulation was carried out. The proposed integrated simulation was applied to the injection molding of a rectangular strip containing micro channels, and the resulting mold heating capacity and replication characteristics of the micro channels were compared with experimental findings in order to verify the validity of the proposed simulation.
사출성형시 굴절율 변화를 고려하기 위한 플라스틱 비구면렌즈의 광선추적기법
엄혜주(Hyeju Eom),박근(Keun Park) 한국소성·가공학회 2009 소성가공 : 한국소성가공학회지 Vol.18 No.2
The present study covers an integrated simulation method to evaluate optical performance of an aspheric plastic lens by connecting an injection molding analysis with a ray tracing simulation. Traditional ray tracing methods have based on the assumption that the optical properties of a lens are homogeneous throughout the entire volume. This assumption is to a certain extent unrealistic for injection-molded plastic lenses because material properties vary at every point due to the injection molding effects. To take into account the effects of the inhomogeneous optical properties of the molded lens, a numerical scheme is developed to calculate the distribution of refractive index induced from the injection molding process. This index distribution is then reflected onto CODE V<SUP>®</SUP> simulation and used to calculate ray paths in inhomogeneous media. The proposed tracing scheme is implemented on the tracing of an aspheric lens for a mobile phone camera module.
열-유동 상호작용을 고려한 유도가열 적용 미세 사출성형의 통합적 수치해석
엄혜주(Hye Ju Eom),박근(Keun Park) 대한기계학회 2010 大韓機械學會論文集A Vol.34 No.5
최근 박육사출성형이나 마이크로 사출성형에서의 성형성을 높이기 위해 급속 금형가열 기술이 사용되고 있다. 고주파 유도가열은 전자기 유도현상을 이용하여 금형 표면만을 효율적으로 가열할 수 있어 급속 금형가열 기술로서 활용되고 있다. 본 연구에서는 고주파 유도가열 적용 사출성형 과정의 수치적 모사를 위해 전자기장 해석, 열전달 해석, 사출성형 유동해석을 연계한 통합적 전산모사 기법에 관한 연구를 수행하였다. 본 연구에서 제안된 통합적 전산모사 기법을 유도가열 적용 박육 사출성형의 해석에 적용하여 실험결과와 비교하였고, 특히 금형온도 경계조건의 부여방식에 따른 해석의 신뢰성에 대한 고찰이 이루어졌다. In recent years, several rapid-mold-heating techniques that can be used for the injection molding of thin-walled parts or micro/nano structures have been developed. High-frequency induction heating, which involves heating by electromagnetic induction, is an efficient method for the rapid heating of mold surfaces. The present study proposes an integrated numerical model of the high-frequency induction heating process and the resulting injection molding process. To take into account the effects of thermal boundary conditions in induction heating, we carry out a fully integrated numerical analysis that combines electromagnetic field calculation, heat transfer analysis, and injection molding simulation. The proposed integrated simulation is extended to the injection molding of a thin-wall part, and the simulation results are compared with the experimental findings. The validity of the proposed simulation is discussed according to the ways of the boundary condition imposition.
박근,엄혜주,안종호,Park, Keun,Eom, Hyeju,Ahn, Jong-Ho 한국금형공학회 2012 한국금형공학회지 Vol.6 No.1
In order to produce high-quality optical components, aspheric lenses have been widely applied in recent years. An aspheric lens consists of aspheric surfaces instead of spherical ones, which causes difficulty in the design process as well as the manufacturing procedure. Although injection molding is widely used to fabricate optical lenses owing to its high productivity, there remains lots of difficulty to determine appropriate mold design factors and injection molding parameters. In the injection molding fields, computer simulation has been effectively applied to analyze processes based on the shell analysis so far. Considering the geometry of optical lenses, a full-3d simulation based on solid elements has been reported as a reliable approach. The present work covers three-dimensional injection molding simulation and relevant deformation analysis of an injection molded plastic lens based on 3d solid elements. Numerical analyses have been applied to the injection molding processes of three aspheric lenses for an image sensing module of a mobile phone. The reliability of the proposed approach has been verified in comparison with the experimental results.
신호석(H. S. Shin),엄혜주(H. J. Um),박근(K. Park),김영석(Y. S. Kim),김충석(C. S. Kim) 대한기계학회 2007 대한기계학회 춘추학술대회 Vol.2007 No.10
A harmonic gear drive is a compact mechanical device guaranteeing high mechanical advantage and speed reduction. The harmonic drive operates on the principle of flexible-body mechanics, from which we can obtain high torque transmission capability in a single stage. The harmonic drive mainly consists of a wave generator, a flexspline, and a circular spline. Among these components, the flexspline plays an important role in operating the flexible-body mechanics. It is a thin cup-shaped feature containing teeth profile, and usually manufactured in metal. The present study aims to develop a flexspline for a plastic harmonic drive so as to reduce the part weight as well as manufacturing cost. A structural finite element (FE) analysis is carried out in order to verify the structural safety of the plastic flexspline under given deformation conditions. A nonlinear FE analysis considering a deformable body contact is also performed to investigate the contact stress between the teeth of the flexspline and the circular spline.